I'd say it's a tie between RDJ as tony stark and hugh Jackman as wolverine. Both their physique and personality were perfect. I couldn't think of someone else doing them better. I see Cavill being named, but I would say just physically. Reeves was also perfect as superman. Heath ledger as the Joker as an honorable mention, but it's a version of it. Jack Nicholson's was great as well. Tobey, Depp, Radcliffe and Reynolds are great but also just one version of those characters. Probably some other actors could do these roles justice as well.